In display systems employing spatial light modulators, such as micromirror-based spatial light modulators, liquid-crystal-display (LCD) panels, and liquid-crystal-on-silicon (LCOS) panels, etc., color images are often produced using sequential-color techniques. A typical sequential color technique generates a set of selected color light (e.g. red, green, blue, white, or any combinations thereof) and sequentially illuminates the spatial light modulator with the selected color light. Pixels of the spatial light modulator sequentially modulate the color light and produce the desired color image.
When spinning color wheels (or other moving sequential color devices) with transmissive (or reflective) color segments are used for generating the selected colors, boundaries of adjacent color segments in the spinning color wheel are imaged onto the pixel array of the spatial light modulator. The image of the boundary at the pixel array is often referred to as “spoke.” As the color wheel spins, the spoke moves across the pixel array of the spatial light modulator. The time interval of the spoke sweeping across the entire pixel array (e.g. from the bottom to the top of the pixel array) is referred to “spoke time.” During the spoke time, pixels of the spatial light modulator being swept by a spoke are illuminated by light of different colors; and these pixels can not be used for displaying pure colors. As a consequence, the total amount of time for displaying pure colors is decreased, resulting in decrease of the pure color efficiency. In this disclosure, a pure color is referred to as a color generated by a single color segment of a color wheel. The term “mixed color” or “color mixture” will be used to represent a combination of pure colors, each of which is generated by a single color segment of a color wheel.
There exist multiple approaches (which are referred to as spoke-chasing or spoke synchronization techniques) for utilizing the spoke time so as to improve the system performance and efficiency. However, these approaches are not compatible with lamp-pulsing techniques.
Lamp-pulsing techniques have been recognized as effective methods for increasing bit-depths of display systems, as well as overall system brightness, despite the mechanical limitations of the spatial light modulators employed in the display systems; and are growingly used in display systems. Current lamp-pulsing techniques, however, may not be compatible with existing spoke-chasing techniques.
Therefore, it is desired to develop a spoke-chasing technique that allows for lamp-pulsing during operation.